1. Field of the Invention
The present invention relates generally to idle speed control systems for internal combustion engines in automotive vehicles and, more particularly, to a method of diagnosing an idle speed control system for an internal combustion engine in an automotive vehicle.
2. Description of the Related Art
It is known to provide an internal combustion engine of an automotive vehicle with an idle speed control system. Typically, the idle speed control system has an Automatic Idle Speed (AIS) motor which controls the amount of idle air in a throttle body of the internal combustion engine. Typically, the idle speed control system is diagnosed by checking for an open or short in a circuit of the AIS motor.
One disadvantage of the above diagnostic routine is that the AIS motor can loose control although the circuit to the AIS motor is closed. Another disadvantage of the above diagnostic routine is that only an electrical problem is diagnosed.